Method of stabilizing milk and product thereof.



G. W. MQMULLEN. METHOD OF smmmzme MILK AND-PRODUGT THEREOF. APPLICATION FILED MAR. 31, 1913. 1,086,385, Patented Feb: 10, 1914.

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WITNESSES G. W. MoMULLEN.

METHOD OF STABILIZING MILK AND PRODUCT THEREOF.

APPLIUATION FILED MAR. 31, 1913.

Patented Feb. 10, 1914.

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' STATES PATENT OFFICE.

GEORGE W. MOMULLEN, OF PISTON, ONTARIO, CANADA.

METHOD OF STABILIZING MILK AND PRODUCT THEREOF.

Specification of Letters Patent.

Application filed March 31, 1913. Serial No. 157,919,

in is a specification.

- his-invention relates to methods of treating milk, and 'to the products thereby formed, the primary object of the invention I being the conversion of milk, without alteration of its essential or normal qualities and without the addition of any foreign substance or material, into a commercially stable form, that is to say,--into a form in which it is capable of enduring exposure to air for a considerable period, as several days, without appreciable deterioration.

I' have found that living organisms which are always present in commercial fresh milk and which, by their growth and multiplication, quickly bring about the deterioration of such milk, may, under certain conditions as hereinafter defined, be destroyed or rendered inactive at temperatures below that at which there occurs any appreciable ooagulat-ion of the milk proteids, or any alppreciable modification or alteration of t e milk, affecting its essential qualities with respect to taste, di estibility or nutritive value. These results I o tain by subjecting the milk for a period a proximating one hour to a temperature be. o-w that at which the milk proteids are coa ulated, that is to say, below 140 F., but so ciently high to practically destroy all the bacteria of a disease or putrefaction-producing character without completely destroying the lactic acid bacteria. WVhen temperatures of 140 F. and over are used as in pasteurization or sterilization, the milk undergoes more or less profound changes, which it is the purpose of the present invention to avoid. For example, at such higher temperatures, there occurs a coagulation of prot-eid matters and perhaps other physical or chemical modifications of the milk solids with the result that the treated milk is unsuited for the manufacture of cheese by the usual methods. Further, the ultimate deterioration of milk so treated is found in many cases at least to be putrefactive in character, as distinguished from swung by lactic acid fermentation, indicatmg that at temperatures above 140 F., a

practically complete destruction of the lactic acid bacilli of the fresh milk is accomplished. Results similar to the foregoing are also found to follow a too prolonged exposure at temperatures somewhat below 140.

It is generally understood that coagulation of albuminoids begins at about C. or 140 F. To successfully operate my invention it is not necessary to heat the milk to so high a temperature, as I ave found preferable results'at temperatures onsiderably lower. I have proved that a lengthened treatmentat a lower temperature will pro-' duce practically the same low bacteria count as a shorter treatment at a higher temperature. The temperature must be above the thermal death point of the bacteria tobe eliminated and the time of treatment should not be lengthened beyond what is reasonable and economical in a commercial process.

Patented Feb. 10, 1914.

Milk treated in accordance with the present invention shows no coagulation of proteids or other appreciablephysical or chemical modifications of the normal milk solids, is perfectly adapted fort-he manufacture of butter and cheese, undergoes ultimately a normal lactic fermentation, and, in general, exhibits the normal properties of fresh milk, while possessing in addition to these normal properties, a degree of stability which enables it to be preserved at ordinary temperatures and with special precautionary methods for several days. I have found that these results can be obtained by heating milk for a period of about forty-five or fifty minutes, at a temperature well below 140 F., that is, at from 130 to 135 F., and that by such treatment, the objectionable bacteria-content of the milk has been reduced to a very minute percentage of that in the raw milk, while not all the lactic acid bacteria have been destroyed. The bacterial growth in milk thus treated appears to remain practically stationary for several days, after which the growth recommences, but some days elapse befOre the bacteria count reaches that of the fresh milk before treatment; and when the milk finally so-urs and curdles, it develops the natural healthy lactic acid curd without putrefaction.

I have obtained the most favorable results by carrying out the process under such conditions that the milk is heated in an atmosphere as nearly as practicable saturated with respect to moisture, although my invention is not limited to such procedure.

Reference is made to the accom anying drawings, illustratmg a preferred orm of apparatus, it being understood, however,

that the use of apparatus such as is herein described, is not essential for carrying out the invention.

In 'said drawingsFigure 1 is a central longitudinal section of the apparatus, show ing the rotary disks in elevation, parts being broken away; and Fig. 2 is a transverse section "of the same on line 11-11 of Fig. 1.

, f In said drawings, 1 indicates a semi-cylintemperature of the contents of the trough 1 ation.-

drical trough or receptacle, supp0rted by side-bars 2 within an outer casing 3 which is provided with a cover 4. The whole. is carried by any suitable framework 5. As illustrated, the casing 3 is provided with a bottom port-6 and with a series of cover ports 7, any or all of which may be provided with removable covers 8. Between the trough 1 and the casing 3 is a series of closed steam-coils 9 by means of which the may be accurately controlled. A shaft 10 extends longitudinally through the trough and casing, and hasrigidly mounted thereon, in said trough, a series of vertical, closelyspaced disks 11. A movement of rotation may be imparted to the shaft 10 by any The operation ma be successfully prac tised as follows:' ommercialfresh milk,

preferably brought up to a temperature of about 130 in a preheating device, is introduced into the trough or receptacle 1, and the disks 11 set in motion at a speed of to revolutions per minute, or at such higher or lower rate, having due regard to the diameter of the disks, as may safely be imployed without danger of separation of at. preferably the ports 7 in thecover, or certain of them, are closed, the conditions being so adjusted as to maintain a temperature in the milk preferably of from 130132, or not greatly exceeding 135 F., and a degree of humidity in the interspaces between the disks 11 in excess of. per cent, and preferably in excess of per cent. Such conditions are maintained for about one hour or less, or until the milk has acquired the Steam is admitted to the coils 9, and.

ess, the following results were obtained by treating the milk for 45 minutes at F. Sample No. 1: Morning milking treated at 10 a. m. Fresh milk 300,000 bacteria per cc. Treated milk 2,000 and 2,200 bacteria per cc.

Sample No. 2: Morning milking treated at 8 a. m. Fresh milk 27,500 bacteria per cc. Treated milk 300 and 400 'baoteria er cc.

p Sample No. 3: Mixed'night and mornin milking from cheese factory. Fresh mili 4,000,000 bacteria per cc. Treated milk 5,000 and 5,400 bacteria per cc.

All these samples remained practically stationary as regards bacteria count for three days. Sample No. 3 was transported in a railwaycar for twelve hours andwas then kept at a temperature of from 48 to 55 F. At the end of thirteen days it was sweet and normal With a bacterial count of a little over 500,000 per cc. The other samples showed equally good results.

: It is to be understood that "the principal factors affecting the treatment, to wit, the temperature of the milk, the time of treat- ;ment, and the degree of saturation of the atmosphere adjacent the exposed surfaces ,;of the milk, may be varied within certain limits and with proper correlation. Thus the time of treatment for sterilization is determined with respect to the stability of the product, milk which will endure exposure to air for three to five days without material increase in acidity being deemed commercially stable within the meaning of this application. The temperature of the milk during treatment should in no case be suificiently high to efiect coagulation of the milk proteids within the time required 'for commercial stabilization. Temperatures of F. or slightly higher have been found to be safe in this respect; slightly lower temperatures, as 130132 F., are in most cases preferred as yielding the most satisfactory results as regards stabilization without danger of afiecting the condition or character of the normal milk solids. The temperature should be sufliciently high to main- Milk treated as above described possesses, substantially the flavor, taste and consistence of norma'l milk, remains sweet and wholesome for a period amply sutlicient for its distribution to and utilization by consumers at localities far removed fromthe center of production and treatment.

Very rapid evaporation is inconsistent with effective stabilization of the milk in accordance with this invention, since such rapid evaporation necessarily involves the use of-large volumes of unsaturated air or gas. It is however often desirable in practice to concentrate the milk to a greater or less degree and such concentration isreadily and economically effected, after the milk has been pro erly stabilized, by increasing the volumeof air, as by opening the ports 6, 7, or by otherwise causing a current of air to flow in contact with the exposed surfaces of the milk: This phase of the treatment need not differ essentially from milk-evaporation as heretofore practised, it being necan essary only that the temperature of the .milk

should be maintained throughout the treatment below that temperature at which any coagulation by heat of the milk proteids occurs. Temperatures of 135 F. or slightly higher are satisfactory. The ,final product may be either a thickened liquid or a homogeneous, semi-solid mass having a consistence similar to that of butter or of green cheese, but difi'ering fundamentally from these in that it contains the normal milk solids'in the same relations in which they exist in the normal milk. For instance by concentrating the milk to slightlyless than 20. per cent. of its original bulk, or by evaporating about 80 pounds of water from each 100 pounds of original milk, a palatable, readily-digestible and commercially sterile product is obtained. 7

' he process is equally applicable to fresh milk and to skimmed milk, with a corresponding difference in the com osition of the product. Also, the milk, after having been stabilized in the manner described, may

- be treated as usual for the separation of cream, and eitheror both of the separated stabilized products may then undergo further concentration.

I believe myself-to be the first to effect the stabilization or commercial sterilization of milk, without foreign agencies, by treatment for a sufficient but not excessive time at a temperature, so low as not materially to afiect the proteids'or other normal milk solids, but above the necessary thermal death point of disease and other bacteria to 'be eliminated.

In practice, I have in certain cases maintained the practical saturation of the atmospherein contact with the surface of the milk until the concentration has proceeded as far as desired, even to a semi-solid or buttery consistence. This insures, under,v all conditions, a stable, safe and highly palatable product; nevertheless, after the material has been stabilized under the described con- .methods above described, by' ordinary sepadition of substantial saturation, it is quite practicable to effect the concentration with a material reduction of the degree of saturation of the surrounding atmosphere,the evaporation being thereby greatly expedited. Further, when milk, properly agitated, as by the use of the above apparatus, is subjected for from 45 to 50 minutes to a temperature of about 131 F., all tvphoid and tuberculosis bacteria are either destroyed or rendered innocuous, vso that my method is also effective against these-disease bacteria,

if present. I have further found that cream taken from milk treated according to-the ration, will keep sweet for practically the same length of time as the whole milk undersimilarconditions, and that the cream treated at this temperature is unchanged in character, giving the possibility of maintaining g5: cream in its sweet natural state for from a week to ten days. at temperatures of from 48 to 55 F. It will be understood therefore that by theterm milk, as used in the claims, is meant either whole milk or skimmed milk, concentrated -or unconcentrated, or cream.

I claim: t 1. The method 'of preparing stabilized normal milk, which consists in heating milk 96 to a temperature below 140 Fahrenheit, the treatment being sufficiently prolo ed and under proper conditions to effect t e commercial stabilization of the milkwithout coagulation of the milk proteids. Q 100 2. The herein-described method ofstabilizing milk, which consists in exposing the same at a temperature below that at which, coagulation of the milk proteids occurs, to an atmosphere substantially saturated'with aqueous vapor, the exposure being sufii- .ciently prolonged to accomplish the commercial stabilization of the milk;

3. The method of preparing stabilizednormal milk, which consists in heating, milk to a temperature below 140 Fahrenheit, the the treatment being sufficiently prolongedand under proper conditions to effect the commercial stabilization of the milk without coagulation of the milk proteids, and there after separating the cream from the milk, whereby two commercially stable products are produced.

4. The herein-described method of stabilizing milk, whichconsists in exposing the same at a tem erature approximating but, below that atw ich coagulation of the milk proteids occurs, to an atmosphere substan-- tially saturated with aqueous vapor, the exposure being sufficiently prolonged to accomplish the-commercial stabilization of the I milk, and thereafter separating the cream I from the milk, whereby two commercially stable. products are produced.

its

5. As a new article manufacture, milk.

in a' commercially stable condition, capable of withstanding exposure for several days without material chan free from antise tic substances, containing the normal mi k soli unaltered in physical or chemical condition, possessing practically the taste and flavor of fresh m1lk and adapted for the pre aration of butter or cheese by usual dition, possessing met 1 ods.

6. As a newarticle of manufacture, milk in a commercially stable condition, capable of withstanding exposure for several days without material change, free from antiseptic substances, containing the normal milk of withstanding exposure for several days without material change, free from antiseptic substances, but containin lactic acid bacteria, havingthe normal milk solids un-' altered in physical or chemical condition, possessing practicall of fresh milk and a apted for the preparethe taste anda-fiavor tion of butter or cheese by usual methods.- V

stabilization of the milk without coagulation of the milk proteids.

In testimony whereof I aflix my signature in presence of two witnesses.

' GEORGE W. MoMU'LLEN. Witnesses:

H. C. MCMULLEN, G. B. MoMULmN.

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